After decades of mandatory rules, regulators in the U.S. and Europe are taking a more flexible, industry-friendly approach

BRUSSELS—Air-safety regulation is changing dramatically on both sides of the Atlantic, increasingly shifting from mandatory rules to voluntary standards dependent on enhanced government and industry collaboration that already has seen accident rates fall world-wide.

Capping years of gradual movement toward such cooperation, the more flexible, industry-friendly approach was spelled out this week by speakers at an international aviation conference in the Belgian capital. Senior European and U.S. regulators emphasized that formal,...